Chocolate Gelato

Hi, Hannah. I forwarded your question to Chef Russ, as ice cream ingredient technology is one of his specialties.

The short answer is you can use a milk protein powder, one that is 100% whey and casein, or possibly even pea, potato, or egg white protein.

I'm going to paste his full answer below so you can have all the inside information ;)

Proteins in ice cream, primarily caseins (80%) and whey proteins (20%), contribute to its texture and stability through emulsification, aeration, and solution behavior. They stabilize fat droplets in the mix, enabling smoothness and melt resistance, and promote partial fat coalescence during freezing to improve texture. Proteins also aid in foam formation by stabilizing air bubbles, enhancing the creamy mouthfeel. Additionally, their water-holding capacity boosts viscosity, providing body and slowing meltdown. By minimizing ice crystal growth during freezing, they ensure a smooth texture and firmness, leading to better sensory qualities and texture stability over time.

Protein in this recipe could refer to any wide variety of protein powders available on the market. Milk protein powder (100% casein+whey) would be the best option, however, pea, potato, or even egg white powder could be used. Each one behaves a little bit differently, but not having created the referenced recipe, I would assume milk protein is intended.